尝试在已经呈现 (null) [Swift] 的视图控制器上呈现 UIAlertController [英] Attempt to present UIAlertController on View Controller which is already presenting (null) [Swift]
问题描述
我有一个警报视图，我正尝试在照片视图中显示该视图.
I have an alert view that I am trying to present on a photo view.
照片显示在列表中，可以推送到全屏视图.
The photos are displayed in a list and can be pushed to a full-screen view.
照片视图正在以编程方式显示.我认为这就是导致问题的原因，因为警报视图试图在已经呈现的(照片)视图之上呈现另一个视图.
The photo view is being displayed programmatically. I think that is what is causing the issue because the alert view is trying to present another view, on top of the (photo) view that's already presented.
警报视图正在尝试显示，但收到此错误:
The alert view is trying to display, but getting this error:
Warning: Attempt to present <UIAlertController: 0x147d2c6b0> on <LiveDeadApp.ListViewController: 0x147d614c0> which is already presenting (null)
可能有问题的那一行是:
The line that might be in question is this one:
self.present(textPrompt, animated: true, completion: nil)
这是主列表视图
这是截屏时的主列表视图
This is the main list view when a screenshot is taken
这是主照片视图
这是主照片视图中的弹出窗口(通过i"按钮访问)
在主照片视图上截取屏幕截图时，不会出现警报视图.但是，当设备的方向发生变化时，照片视图会返回到列表并显示警报.
这就是我想要做的:
iOS 10 中的 Swift 3
Swift 3 in iOS 10
谢谢！
这是列表视图和照片视图的代码:
Here is the list view and photo view's code:
import UIKit
import Kingfisher
import SKPhotoBrowser
class ListViewCell: UITableViewCell {
@IBOutlet weak var Cellimage: UIImageView!
@IBOutlet weak var cellVenue: UILabel!
@IBOutlet weak var cellLocation: UILabel!
@IBOutlet weak var cellDate: UILabel!
@IBOutlet weak var aiView: UIActivityIndicatorView!
}
class ListViewController: UITableViewController {
var subcategory:Subcategory!
var objects:[[String:String]] = [[String:String]]()
var images = [SKPhotoProtocol]()
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
}
override func viewDidLoad() {
super.viewDidLoad()
self.tableView.separatorStyle = .none
self.view.backgroundColor = UIColor.black
self.navigationController?.navigationBar.titleTextAttributes = [NSForegroundColorAttributeName: UIColor.white]
navigationController!.navigationBar.barTintColor = UIColor.black
let requireTextInput = "require text input"
// add observer for screen shot
NotificationCenter.default.addObserver(forName: NSNotification.Name.UIApplicationUserDidTakeScreenshot, object: nil, queue: OperationQueue.main, using:
{ notification in
self.definesPresentationContext = true
var inputTextField = UITextField()
let textPrompt = UIAlertController(title: "Test!", message: "Testing!", preferredStyle: .alert)
textPrompt.addAction(UIAlertAction(title: "Continue", style: .default, handler: {
(action) -> Void in
// if the input match the required text
let str = inputTextField.text
if str == requireTextInput {
print("right")
} else {
print("wrong")
}
}))
textPrompt.addTextField(configurationHandler: {(textField: UITextField!) in
textField.placeholder = ""
inputTextField = textField
})
self.present(textPrompt, animated: true, completion: nil)
})
if subcategory != nil {
self.title = subcategory.title
self.objects = subcategory.photos
createLocalPhotos()
self.tableView.reloadData()
}
}
func createLocalPhotos() {
for item in objects {
let photo = SKPhoto.photoWithImageURL(item["url"]!)
photo.shouldCachePhotoURLImage = true
images.append(photo)
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
override func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return objects.count
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell: ListViewCell = tableView.dequeueReusableCell(withIdentifier: "Cell") as! ListViewCell
let item = objects[indexPath.row]
let title = item["title"]
let location = item["location"]
let date = item["date"]
let urlSrt = item["url"]
cell.cellVenue.text = title
cell.cellLocation.text = location
cell.cellDate.text = date
if let url = URL(string: urlSrt!) {
cell.aiView.startAnimating()
cell.Cellimage.kf.setImage(with: url, placeholder: nil, options: nil, progressBlock: nil, completionHandler: { (image, error, cacheType, url) in
cell.aiView.stopAnimating()
})
}
return cell
}
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
let cell = tableView.cellForRow(at: indexPath) as! ListViewCell
if(cell.Cellimage.image != nil ) {
SKPhotoBrowserOptions.displayToolbar = false
SKPhotoBrowserOptions.displayCounterLabel = false
SKPhotoBrowserOptions.displayBackAndForwardButton = false
SKPhotoBrowserOptions.displayAction = false
SKPhotoBrowserOptions.displayDeleteButton = true
SKPhotoBrowserOptions.displayHorizontalScrollIndicator = false
SKPhotoBrowserOptions.displayVerticalScrollIndicator = false
SKPhotoBrowserOptions.displayStatusbar = false
SKPhotoBrowserOptions.disableVerticalSwipe = true
SKPhotoBrowserOptions.bounceAnimation = false
let browser = ExtendedSKPhotoBrowser(originImage: cell.Cellimage.image!, photos: images, animatedFromView: cell)
let btnSize = 80//24 * UIScreen.main.scale
browser.updateCloseButton(UIImage(named: "ic_close_white")!, size: CGSize(width: btnSize, height: btnSize))
browser.updateDeleteButton(UIImage(named: "ic_info_white")!, size: CGSize(width: btnSize, height: btnSize))
browser.initializePageIndex(indexPath.row)
browser.delegate = self
present(browser, animated: true, completion: {})
browser.toggleControls()
}
}
override var prefersStatusBarHidden: Bool {
get {
return true
}
}
var popOverVC:PopUpViewController!
}
extension ListViewController: SKPhotoBrowserDelegate {
func didShowPhotoAtIndex(_ index: Int) {
}
func willDismissAtPageIndex(_ index: Int) {
}
private func willShowActionSheet(photoIndex: Int) {
// do some handle if you need
}
func didDismissAtPageIndex(_ index: Int) {
}
func didDismissActionSheetWithButtonIndex(_ buttonIndex: Int, photoIndex: Int) {
// handle dismissing custom actions
}
func removePhoto(_ browser: SKPhotoBrowser, index: Int, reload: (() -> Void)) {
popOverVC = self.storyboard?.instantiateViewController(withIdentifier: "sbPopUpID") as! PopUpViewController
popOverVC.photoData = objects[index]
}
func viewForPhoto(_ browser: SKPhotoBrowser, index: Int) -> UIView? {
return tableView.cellForRow(at: IndexPath(row: index, section: 0))
}
}
open class ExtendedSKPhotoBrowser: SKPhotoBrowser {
open override var preferredStatusBarStyle: UIStatusBarStyle {
return .lightContent // white statusbar, .default is black
}
open override var prefersStatusBarHidden: Bool {
return true
}
}
推荐答案
问题很简单，你试图在当前呈现的 UIAlertController 上显示另一个 UIAlertController.
The problem is really simple, you are trying to display another UIAlertController on the currently presented UIAlertController.
那么，如何解决这种情况?
您需要获取当前视图控制器中使用的所有
UIAlertController的列表.
You need to get a list of all
UIAlertController's you use in your current view controller.
您必须检查在当前视图控制器(或其他视图控制器，如果您正在执行异步请求)中显示警报的逻辑.
当您想在另一个警报之上显示一个警报时，您的代码必须是这样的.
假设 loadingAlert 当前显示在屏幕上:
Assume loadingAlert is currently displaying on the screen:
self.loadingAlert.dismiss(animated: true, completion: {
let anotherAlert = UIAlertController(title: "New One", message: "The Previous one is dismissed", preferredStyle: .alert)
let okAction = UIAlertAction(title: "OK", style: .default, handler: nil)
anotherAlert.addAction(okAction)
self.present(anotherAlert, animated: true, completion: nil)
})
您必须先关闭第一个，然后才能出现下一个.我做了这个回答是为了消除没有按钮的警报以提高效率.
You have to dismiss the first one before the next one can appear. I made this answer for dismissing an alert without buttons on it to make it more efficient.
那么，带有操作按钮的警报呢?
当您单击其中一项操作时它会自动关闭您创建的 UIAlertController 上的按钮.
It will dismiss automatically when you click one of the action
buttons on UIAlertController that you created.
但是，如果您同时显示两个包含 UIButton 的 UIAlertController ，问题仍然会出现.您需要重新检查每个操作的逻辑，或者您可以在每个操作的处理程序中处理它:
But, if you are displaying two UIAlertControllers which include UIButtons at the same time, the problem will still occur. You need to re-check the logic for each, or you can handle it in the handler for each action :
self.connectionErrorAlert.dismiss(animated: true, completion: {
let anotherAlert = UIAlertController(title: "New One", message: "The Previous one is dismissed", preferredStyle: .alert)
let okAction = UIAlertAction(title: "OK", style: .default, handler: {action in
let nextAlert = UIAlertController(title: "New One", message: "The Previous one is dismissed", preferredStyle: .alert)
self.present(nextAlert, animated: true, completion: nil)
})
anotherAlert.addAction(okAction)
self.present(anotherAlert, animated: true, completion: nil)
})
回答迈克:
DispatchQueue.main.async(execute: {
if self.presentedViewController == nil {
print("Alert comes up with the intended ViewController")
var inputTextField = UITextField()
let textPrompt = UIAlertController(title: "Test", message: "Testing", preferredStyle: .alert)
textPrompt.addAction(UIAlertAction(title: "Continue", style: .default, handler: {
(action) -> Void in
// if the input matches the required text
let str = inputTextField.text
if str == requireTextInput {
print("right")
} else {
print("wrong")
}
}))
textPrompt.addTextField(configurationHandler: {(textField: UITextField!) in
textField.placeholder = ""
inputTextField = textField
})
weakSelf?.present(textPrompt, animated: true, completion: nil)
} else {
// either the Alert is already presented, or any other view controller
// is active (e.g. a PopOver)
// ...
let thePresentedVC : UIViewController? = self.presentedViewController as UIViewController?
if thePresentedVC != nil {
if let _ : UIAlertController = thePresentedVC as? UIAlertController {
print("Alert not necessary, already on the screen !")
} else {
print("Alert comes up via another presented VC, e.g. a PopOver")
}
}
}
})
感谢@Luke 回答:https://stackoverflow.com/a/30741496/3378606
Thanks to @Luke Answer : https://stackoverflow.com/a/30741496/3378606
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